Lambs with six legs happen every once in a while. This first story is from 2006:
A lamb with six legs, four in front and two at the back, has been born on a farm in Belgium, the news agency Belga reported today. The lamb cannot walk and has to be specially fed. A veterinary surgeon who examined it was reported as saying he would consider amputating the two superfluous legs to give the animal a normal existence if it managed to survive beyond a week.
Here’s another from 2012: “A Geor
gian farmer is the talk of his village after one of his sheep gave birth to a lamb with six legs. The piebald lamb has four legs at the front and two at the back. (Jan. 25)”
The lamb was born in the village of Velistsikhe. Shepherd Albert Abadzhanov said that the animal is having a little trouble walking but seems to be getting the hang of it. Abadzhanov said:“I have been asking the other shepherds, but none of them remember such [a] case. There were three-legged lambs, one-eyed, but not [a] six legged … (AP)
Here is a third case dated March 28, 2019, from Bosnia, although it may not be from this year.
When Meho Avdic saw his sheep was struggling to give birth two weeks ago, he kneeled down to help but then saw something he never saw before – the newborn had six legs.
“When I saw the lamb, I couldn’t believe it, it had six legs,” said Avdic, who has been keeping sheep in his village of Budak, near the eastern town of Srebrenica, since he was a child.
One theory for the cause of six legged lambs is that they are fused twins, where one animal developed completely and the other appears as extra parts. The blueprints to make any animal is encoded in DNA and during the amazing complicated process after and including fertilization, unexpected things sometimes happen.
This makes 6 legged sheep a specific type of conjoined twins, where one twin ceases development during gestation and becomes vestigial to the fully formed dominant twin, called the autositic twin. The underdeveloped twin is only partially formed, is not functional, or is wholly dependent on the autositic twin. This is not the only option, however.
Protein Over Expression Theory
A protein with the interesting name Sonic Hedgehog (SHH) may be involved.
The SHH gene provides instructions for making a protein called Sonic Hedgehog. This protein functions as a chemical signal that is essential for embryonic development. Sonic Hedgehog plays a role in cell growth, cell specialization, and the normal shaping (patterning) of the body.
A deficiency of SHH during development leads to stunted midline development, and disorders such as fused eyes (cyclopia), a brain lacking hemispherical separation (holoprosencephaly), and fusion of the legs and feet (sirenomelia). Conversely, an increase in SHH during development leads to an over-expression of midline features. In chick embryo experiments, an increase in SHH led to larger than usual spacing between the eyes and duplication of beaks, a condition sometimes referred to as craniofacial duplication. The duplication of features associated with parasitic twinning may be caused by an over-expression of SHH rather than the result of incomplete twinning.
How does Sonic Hedgehog work?
The Sonic hedgehog protein, built from 462 amino acids is a morphogen, a molecule that diffuses to form a concentration gradient and has different effects on the cells of the developing embryo depending on its concentration.
In mammals, lambs as well as humans, SHH is important lifelong with its role in cell division, particularly of stem cells.
The Hedgehog signaling pathway is one of the key regulators of animal development and is present in all bilaterians. The pathway takes its name from its polypeptide ligand, an intercellular signaling molecule called Hedgehog (Hh) found in fruit flies of the genus Drosophila; fruit fly larva lacking the Hh gene are said to resemble hedgehogs.
Without SHH, safe to say, we would not exist. Like every important thing, the right amount in the right place at the right time is what makes it work right.
What causes SHH over-expression?
It may be discovered with more research what causes over expression at the time of limb development. If too much of another protein called p63 is present, that triggers the creation of Sonic Hedgehog, for example.
At this point we still don’t know; it’s a complicated molecular dance researchers are working to understand.
Six legged lambs may turn out to be caused by an environmental factor that triggers a miscommunication in SHH protein signaling during development, but this is just one theory.